Manufacture of electrical devices having sealed envelopes

ABSTRACT

An electrical device, e.g. an electric lightbulb has various electrical and/or optical parts contained inside an envelope, and is made by attaching the various parts to selected fingers of a metal mount which is stiffened by transverse braces interconnecting the fingers, the mount being inserted into and sealed in the envelope so that the braces are inside, and the braces subsequently being breached by the intense heat generated by a beam of laser radiation focussed thereon.

United States Patent Wolfe et a1. 45 s 9, 1975 [541 MANUFACTURE OF ELECTRICAL 3,774,064 11/1973 Vause 313/316 DEVICES HAVING SEALED ENVELOPES 3,817,591 6/1974 Deiss .r 316/19 3,827,142 8/1974 Bennett et a1. H 219/121 LM X [75] Inventors: Kenneth Roy Wolfe; Maurice George Clarke, both of London, England OTHER PUBLlCATIONS [73] Assignee: Thorn Electrical Industries Limited, A. Osial, Industrial Laser Applications, Instruments London England and Control Systems, October 1967, pp. 101104. Adams, Laser Cutting, Engineering Vol. 210, No. [22] 1973 5463, February 1971, pp. 779-782. [21] App]. No: 387,595

Primary ExaminerR0y Lake Assistant Examiner-James W. Davie [30] Foreign Apphc atlon Pnonty Data Attorney, Agent, or FirmRobert F. OConnell Aug. 11, 1972 United Kingdom............... 37646/72 52 us. c1. 313/271; 29/2515; 29/592; [57] ABSTRACT 313/272; 313/315; 316/17 An electrical device, e.g. an electric lightbulb has vari- [51} Int. Cl. HOlJ 1/83; H011 19/42 ous electrical and/or optical parts contained inside an [58] Field of Search 29/2514, 25.15, 25.16, envelope, and is made y attaching the various parts 29/2517, 25.18, 25.1 1, 592; 313/271, 272, to selected fingers of a metal mount which is stiffened 315, 316, 284, 285; 219/121 L, 121 LM; by transverse braces interconnecting the fingers, the 316/17 mount being inserted into and sealed in the envelope so that the braces are inside, and the braces subse- [56] References Cited quently being breached by the intense heat generated UNITED STATES PATENTS by a beam of laser radiation focussed thereon.

3,768.157 10/1973 Buie 65/59 X 8 Claims, 2 Drawing Figures MANUFACTURE OF ELECTRTQAL DEVICES HAVING SEALED ENVELOPES The present invention relates to improvements in the manufacture of electrical devices which incorporate sealed encapsulations or envelopes, such as lamps. valves and the like When making lamps in the past. it has been customary to install supporting wires inside their envelopes. the wires carrying various internal lamp components of an electrical or optical nature Etamples of such components include filaments, shields and reflectors. Some of the supporting wires also serve as current conductors and. are sealed through the lamp envelopes so as to be accessible from the outside. Frequently. it is necessary to locate the filaments of lamps accurately relative to lenses or reflectors in optical apparatus. This requires, inter alia. that the lamps be manufactured to within very small tolerances. It is far from easy to accomplish this by any massproduction technique. since cylindrical wires forming filaments and supporting wires are prone to distortion by shifting. bending and rolling during various phases of the manufacturing process.

Similar difficulties are experienced in making valves which have numerous internal components needing to be attached to supporting wires. The internal components may include filaments. anodes. cathodes. grids and screens. which need be accurately located relative to one another.

To obviate these difficulties. it was found necessary. or at least desirable. to hold the supporting wires firmly together by embedding them permanently in insulating members. for example glass or silica bridges. The stiffening gained thereby prevents mechanical shocks. which may occur whilst attaching the various internal components. attaching external leadin conductors and sealing the envelopes. from distorting the structure.

The aim of the present invention is to improve and simplify the manufacturing techniques by eliminating the need for embedding the support wires in insulating bridge members. whilst still retaining adequate stiffness as a safeguard against distortion.

According to the present invention. there is provided a method of making an electrical device having an enclosing scaled envelope. comprising the steps of making a metallic mounting member having a plurality of fingers which are interconnected by a transverse brace. attaching components of the device to the fingers. loeating the mounting member and the components borne thereby within an envelope, forming a seal be tween the envelope and the mounting member with the transverse brace inside the envelope. and thereafter breaching the brace by focus-sing a beam of radiation from a laser onto the brace so as to isolate selected fingers mechanically and electrically from one another. After breaching the brace. the isolated fingers remain supported within the envelope as a result of being sealed thereto. The exact nature of the internal components depend upon the type of device being made. as indicated hereinbcfore. Once the mounting member has been scaled to the envelope. breaching can be effcctcd at the most convenient point during subsequent finishing stages. It may therefore be preferred to breach the brace at the very end of the manufacturing process. ic. after gasfilling and final closing of the envelope.

Although the mounting member can be fabricated from wires. it is preferred though not essential to make it from sheet metal. A sheet metal blank can be shaped. to define the fingers and brace. by such techniques as pressing. stamping, photo-etching and spark machining. inter alia.

The specific example described hereinafter in detail is a lamp in which the envelope is pinch sealed either directly to the fingers of the mounting member or to in termediate molybdenum foils which are welded to the fingers. Molybdenum foils serve as intermediaries between the fingers and separate lead-in conductors. and are provided to assist in forming reliable seals with the envelope.

lf molybdenum foils and separate leaddn conductors are dispensed with. the fingers are made sufficientlylong that they will project outwardly of the seal. in this case. it may be desirable so to form the mounting memher that the outer ends of the fingers are also provided with a transverse stiffening brace. This brace will help to ensure that the outer ends of the fingers remain pre cisely located with one another before and during seal ing. The stiffening brace is cropped off after sealing.

it will be recognized that the invention can be applied to the manufacture of such lamps as single and twin fil ament vehicle lightbulbs. GLS bulbs. monoplane filament lamps for projectors and the like. as well as to other glass encapsulated devices.

The present invention will now be described by way of example with reference to the accompanying drawings. wherein:

FIG. 1 is a plan view of a filament mount assembly before scaling into an envelope when manufacturing a lamp in accordance with the invention, and

FIG. 2 is a perspective view of a completed lamp.

The completed lamp ]0 shown in FIG. 2 is a doublefilament tungsten halogen vehicle headlamp bulb. of the type known as the H4. The lamp 10 has a tubular envelope of high silica content ll which is sealed at its opposite ends and contains a conventional gas filling including a halogen. Inside the envelope 11 there are two filaments l2. l3 and a reflector or shield 14. The filaments I2, 13 and the shield 14 are supported on a sheet metal mount indicated generally by the reference 16. The mount 16 has three separate fingers or branches l7, l8 and 19. The branches l7, l8 and 19 form current conductors and each is attached to a thin molybdenum foil 20 about which the envelope ll is pinched to form an hermetic seal. The foils 20 are pro vided with sheet metal tails 22 which extend outwardly from the pinch seal 23 for connection to appropriate contacts of a lamp cap (not shown).

The mount 16 is made from any metal which will withstand the operating temperature within the lamp 10. A refractory metal such as molybdenum may be Chosen. The foils 20 can be omitted if desired. in which case the branches l7. l8 and 19 are lengthened as indicated by the chaindashed lines in FIG. 1 so as to embody the tails 22. It may be necessary to reduce the thickness of the branches 1?. l8 and l) locally, in the region of the pinch 23, to assure a mechanically satisfactory seal at elevated temperatures.

The mount 16 is shown in more detail in FIG. 1, and is shaped by any convenient operation such as punching or photo-etching a molybdenum sheet blank. As shown. the fingers or branches l7. l8 and 19 are inter connected intermediate their ends by transverse brac ing portions 31 and 32.

Having punched or photo-etched the mount 16 from a sheet blank, the next step in manufacturing the lamp It) involves attaching the filaments l2, l3 and shield 14 to the mount 16. The shield 14 is a deep-drawn or cupped bowl which is mounted on a molybdenum strip support 34 e.g. by spot welding. One end of the filament 12 is secured and electrically connected to the branch 17 by a member 35 which includes a tang (not shown). The other end of the filament 12 is attached to the branch 18 at its free end by another tang 36 which is bent over to grip the end of the filament 12. The fila ment 13 is secured between the support 34 and the free end of the branch 19 in a similar fashion, i.e., by bending over tangs 37 to grip the ends of the filament 13.

The foils 20 and tails 22 are then secured to the ends 38 of the branches l7, l8 and 19 by welding. This completes the mount and filament assembly which is now ready for inserting into the envelope tube 11. After aligning the inserted assembly with the central axis of the envelope tube 11, the pinch seal 23 is made in the usual way. At this stage, the envelope tube 11 is open at its opposite end 40 and is fitted with an exhaust tube (not shown). The exhaust tube is then attached to a pumping machine and the air is evacuated from the tube 11. Thereafter, the tube is flushed and filled with an appropriate gas, e.g. argon. The exahust tube is then sealed off to leave the exhaust tip seen at the end 40 of the envelope tube 11.

Once the envelope tube 11 has been gas-filled and sealed, the final manufacturing steps can be effected. These steps may include fitting a lamp cap (not shown) to the pinch seal 23 and electrically isolating the fingers or branches 1?, l8 and 19 from one another. The branches 17, 18 and 19 are isolated by severing or breaching the transverse bracing portions 31, 32. These portions are breached by causing the sheet metal to evaporate leaving the gaps 42 seen in FIG. 2. The gaps 42 are formed by focussing a beam of radiation from a alaser onto the portions 31, 32. It has been found that no damage to the envelope tube 11 will result, provided care is taken to ensure that the beam is not focussed on the envelope tube.

It is immaterial at what stage in the manufacturing cycle the branches 17, 18 and 19 are isolated from one another, provided this is done after sealing the mount and filament assembly into the envelope tube 11. It has been found that lamp operation is not deleteriously affected by the evaporation of sheet metal produced while forming the gaps 42.

As mentioned earlier, the foils 20 and tails 22 can be eliminated, for simplicity, in which case the branches 17, 18 and 19 are extended as shown by chain-dashed lines. An additional transverse brace or bridge 45 is desirably attached to the ends of branches as shown to strengthen the mount 16 and enable it to be handled safely. The brace 45 is retained until after the mount and filament assembly has been scaled to the envelope tube 11. The brace 45 is then severed from the branches l7, l8 and 19 along the line 46.

We claim:

1. In the manufacture of an electric device having a sealed enclosing envelope, the steps of:

shaping a sheet metal blank to form a metal mounting member having a plurality of fingers interconnected with integral transverse metal bracing means,

attaching components of said device to said fingers,

inserting said mounting member with said components attached thereto into said envelope whereby said bracing means is located inside said envelope, sealing said envelope, and

thereafter focussing a beam of radiation from a laser onto said bracing means to breach said means and isolate selected fingers mechanically and electrically from each other.

2. The invention claimed in claim 1, wherein said mounting member is shaped by a stamping operation from said sheet metal blank.

3. The invention claimed in claim I, wherein said bracing means is located intermediate the ends of said mounting member and nearer one end thereof than the other, lead out conductors including refractory metal foils being welded to finger ends adjacent said bracing means, and said envelope being sealed to said foils.

4. The invention claimed in claim 1, wherein said bracing means is located intermediate the ends of said mounting member, said mounting member being provided with a transverse bridge at one end thereof which also interconnects said fingers, said mounting member being inserted into said envelope and the latter being sealed directly thereto, said transverse bridge being disposed externally of said envelope and being removed subsequent to said sealing step.

5. An electrical device made by the method claimed in claim 1.

6. An electrical device made by the method claimed in claim 3.

7. An electrical device made by the method claimed in claim 4.

8. A device made by the method claimed in claim 1,

which is a twin-filament, tungsten-halogen lamp. 

1. In the manufacture of an electric device having a sealed enclosing envelope, the steps of: shaping a sheet metal blank to form a metal mounting member having a plurality of fingers interconnected with integral transverse metal bracing means, attaching components of said device to said fingers, inserting said mounting member with said components attached thereto into said envelope whereby said bracing means is located inside said envelope, sealing said envelope, and thereafter focussing a beam of radiation from a laser onto said bracing means to breach said means and isolate selected fingers mechanically and electrically from each other.
 2. The invention claimed in claim 1, wherein said mounting member is shaped by a stamping operation from said sheet metal blank.
 3. The invention claimed in claim 1, wherein said bracing means is located intermediate the ends of said mounting member and nearer one end thereof than the other, lead out conductors including refractory metal foils being welded to finger ends adjacent said bracing means, and said envelope being sealed to said foils.
 4. The invention claimed in claim 1, wherein said bracing means is located intermediate the ends of said mounting member, said mounting member being provided with a transverse bridge at one end thereof which also interconnects said fingers, said mounting member being inserted into said envelope and the latter being sealed directly thereto, said transverse bridge being disposed externally of said envelope and being removed subsequent to said sealing step.
 5. An electrical device made by the method claimed in claim
 1. 6. An electrical device made by the method claimed in claim
 3. 7. An electrical device made by the method claimed in claim
 4. 8. A device made by the method claimed in claim 1, which is a twin-filament, tungsten-halogen lamp. 